<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
		<script>
			function btn2() {
				history.go(-1);
            }
		</script>
	</head>
	<body>
		<h1>我是b页面</h1><br />
		
			<input type="button" value="后退" onclick="btn2()"/>
		
	</body>
	
</html>
